The present invention relates generally to an image recording apparatus for recording a color image on a color developer sheet with the use of a photosensitive and pressure sensitive recording sheet, in which a latent image formed on the photosensitive and pressure-sensitive recording sheet is subjected to a pressure development to provide a visible image on the color developer sheet. More particularly, the invention relates to a thermal fixing device in such an image recording apparatus for thermally fixing the developed visible image on the color developer sheet.
A recording sheet applicable to the image recording apparatus of the invention is disclosed in Japanese Laid-Open Patent Publication No. 58-17432. The recording sheet disclosed therein is in the form of a photosensitive and pressure-sensitive recording sheet coated on one surface with photocuring microcapsules encapsulating dye precursors. An image on n image carrying sheet is recorded on the photosensitive and pressure-sensitive recording sheet as a latent image. The latent image is formed in such a way that microcapsules are selectively photocured corresponding to the image on the image carrying sheet upon exposure to light emitted from an exposure light source and bearing image information. A color developer sheet is then superposed on the recording sheet with the latent image formed thereon, and the two sheets are pressed by a pair of pressure developing rollers. Those microcapsules which have not been photocured are ruptured by the application of pressure, thereby allowing the dye precursors to flow out of the ruptured microcapsules and react with the color developer coated on the color developer sheet Thus, the latent image formed on the photosensitive and pressure-sensitive recording sheet is transferred onto the color developer sheet. The transferred image is then thermally fixed with heat applied to the color developer sheet.
Thermal fixing is carried out in order to speed up color development, improve coloring of the developed image, and to make the image glossy. Ordinary electrophotography employs a thermal fixing device comprising a heating roll and a pressing roll for sandwiching a recording sheet therebetween while heating the same. The thermal fixing device in electrophotographic apparatus requires electric power of at least 900 W. Since, however, a recording apparatus using a photosensitive and pressure-sensitive recording sheet consumes a large amount of electric power for exposure only, the exposure and thermal fixing devices of such a recording apparatus could not be simultaneously energized by a home-use electric power supply.
There has been devised a thermal fixing device using the exposure light source as a heat source for heating the color developer sheet through heat radiation. While such a thermal fixing device is advantageous in that no new separate heat source is required, it is disadvantageous in that a long period of time is needed to thermally fix the image since the heat radiation from the exposure lIght source is low in efficiency. In addition, designing the entire system in order to position the exposure light source and the thermal fixing zone closely to each other has been subject to limitations